Three wolves have been shot dead after a pack of five animals broke through a perimeter fence and escaped into thick undergrowth.

One of the five fugitive wolves returned to the enclosure shortly after the animals broke free around 7.30am.

Another wolf was shot with an anaesthetic dart and recaptured.

Authorities then began a search to locate the three remaining wolves, with Essex Police officers assisting the search operation.

Members of the public were asked to stay away from the search area to avoid hindering the operation.

All three remaining wolves were eventually shot dead after they were located and authorities determined they "posed a risk to the public".

A statement from Colchester Zoo said staff members were "devastated" by the loss of the wolves.

"Unfortunately, an anaesthetic dart takes 15 minutes to take effect and may not work at all in a stressed animal so two wolves that had left the perimeter of the zoo had to be shot," the statement said.

"They are wild animals and in an unpredictable situation they would have posed a risk to the public. The remaining wolf has now been located and very sadly also had to be destroyed."

The zoo said it remains unclear how the damage occurred to the wolf enclosure.

"It is not known at this stage how the damage occurred despite the fence being routinely checked on a daily basis," the statement said.

"We have obviously had a very difficult day and would be grateful for your consideration. We have nothing further to add at this time."

In August, members of the public were warned not to approach a red river hog that went on the run from the zoo.

And in February 2012, horrified members of the public looked on as a "dazed" barn owl flew into the zoo's lion enclosure and was killed.